Onkyo EQ 35 Service Manual

Page 1

EQ-35

SERIAL NO. 3162

ONKYO SERVICE MANUAL

STEREO GRAPHIC EQUALIZER
MODEL EQ-35

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UDN, UD 120V AC, 60Hz
UW 120V or 220V AC, 50/60Hz
TABLE OF CONTENTS
SAFETY-RELATED COMPONENT WARNING

COMPONENTS IDENTIFIED BY MARK A ON Item Page
THE SCHEMATIC DIAGRAM AND IN THE PARTS Specifications 2
LIST ARE CRITICAL FOR RISK OF FIRE AND Block diagram 2
ELECTRIC SHOCK- REPLACE THESE COM' Oscillator distortion adjustment 4
PONENTS WITH ONKYO PARTS WHOSE PARTS Precautions 4
NUMBERS APPEAR AS SHOWN IN THIS MANUAL. . . . .

Circuit description 5
MAKE LEAKAGE-CURRENT OR RESISTANCE Exploded view 6
MEASUREMENTS TO DETERMINE THAT Component location 7
EXPOSED PARTS ARE ACCEPTABLY INfi Using the level control 8
SULATED FROM THE SUPPLY CIRCUIT BEFORE Printed circuit board parts list 9
RETURNING THE APPLIANCE TO THE _ , . .
CUSTOMER. Printed Circuit boaId VIew 11

Schematic diagram 15

Front panel 17

System connections 17

Packing procedures 18

ON KYOO
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Page 4

EQ-35

CIRCUIT DESCRIPTION

Oscillator circuit

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When the mode selector SOURCE pushbutton is pressed,
all level control LEDs (DI-12, D61-72) light. When
SWEEP is pressed, the oscillator circuit (0202 1/4, 0202
2/4) connected to the clock terminal of 0203 begins to
oscillate, the 0203 terminals 01-7 and Q9 go to H in
order and LEDs Dl-l2 and D61-72 light in order
(the lGHz and 32kHz LEDs do not light). Oscillator
sweep is then repeated between 32Hz and 16kHz.

When STOP is pressed, sweep operation stops and the

LEDs light one by one. Each time the SPOT pushbutton .

is pressed, one pulse is applied to the clock terminal of l

0203 and the lighted LED moves to the right one step
at a time up to leH2 after which the 32Hz LED lights
again.

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0288-230 are the built-in oscillator in the graphic
equalizer and 0228 is the oscillator circuit. The output
of 00-9 of 0203 switches FET 0222-226 to switch
the value of C, R. This advances the oscillation
frequency to match each center frequency. During this
procedure, capacity is H when the 00-4 CARRY tenni-
nals of 0203 and H and L when 05-9 are H.

For example, when 02 or 0203 is H, the 125Hz LEDs
light and, at the same time, 0224 is turned on via J2
and the resistance of integrator becomes R217 + R220 +
R221. At this time, CARRY of 0203 is H so 0226 is
turned on via JC, C211 is turned on and a triangular
wave of 125Hz is generated. This triangular wave is then
converted to a similar sine wave by 0229 and 0230.
The semi-fixed resistor VR201 is used to adjust the
distortion of the oscillator.